SAO PAULO (Reuters) - Champions Mercedes plan to use the last two races of the Formula One season to test new ideas and parts for 2018 now that they have won both titles.

The British-based team said in a preview for Sunday's Brazilian Grand Prix that, with nothing at stake, they could afford to become "a little bolder" and experiment in Friday practice.

The experiments could also be carried over into the race for newly-crowned four times world champion Lewis Hamilton and team mate Valtteri Bottas.

"These two final weekends are not only an opportunity to test new parts, but also allow experiments for those tasks that the team simply doesn't have the opportunity to complete during a normal race weekend," said Mercedes.

"The team will have an intense program on the next two Fridays in Brazil and Abu Dhabi to make the absolute most of the opportunities that have been afforded by early title success."

Mercedes won the constructors' championship for the fourth year in a row in Texas last month while Hamilton, now Britain's most successful driver of all time, took his fourth title in Mexico.

Mercedes said they would be using prominent aerodynamic devices, of the type usually seen in pre-season testing and which carry extra weight, in Friday practice.

They will also test some new pit-stop equipment and techniques in live conditions for the first time.

Team boss Toto Wolff said there would be no easing up when it came to racing, however.

"Inside the team, we are looking at the next two race weekends as the first two grands prix of 2018," said the Austrian. "We have two races that we are determined to win in order to take that positive momentum into the winter.

"Every time we race, we race to win. That is the mind set we take to Sao Paulo."